8 MASS. EXPERIMENT STATION BULLETIN 306 



Nitrogen and the minerals were mutually helpful in increasing yields. With 

 the smaller amounts of minerals nitrogen increased yields about 50 per cent, 

 while with the larger applications the yields were more than doubled. Calcium (in 

 limestone), phosphorus, and potassium alone were generally beneficial, but the 

 relative position of each in increasing yields is less certain than in the case of 

 the Worcester experiments. These nutrients were decidedly more effective when 

 applied in various combinations than when used singh. This is especially re- 

 flected in the botanical composition of the clippings. 



In Table 6 the botanical composition of the clippings is given. The efTect of 

 nitrogen in increasing the percentage of grasses is evident, although the percentage 

 of clover remained comparatively high when nitrogen was added to complete 

 mineral treatments. Combinations containing limestone and (or) potassium 

 gave the highest percentage of clover. In some cases, particularly with the 

 heavier applications, the addition of phosphorus further increased the percentage 

 of clover. 



Table 6. — Botanical Composition of Clippings from the Amherst Pasture 



Experiment, 1931 



(Expressed as per cent) 



The toxic effect of sodium nitrate for haircap moss {Polytrichum commune 

 L.) was first noted in Amherst experiment C and was reported in previous publi- 

 cations (1). Further evidence in support of this observation was obtained from 

 the experiments in Worcester County. The toxic effect was definite, and the 

 action cumulative from year to year, so that in the course of four years bad in- 

 festations of this moss were almost or entirely eliminated by moderate applications 

 of sodium nitrate. 



